Diagnosis Of Pregnancy

History

Fact

Explanation

Missed periods

Menstruation is sloughing off of the uterine endometrial lining epithelium as a response to declining pituitary sex hormones (estrogen and progesterone) in the absence of pregnancy, and happens in cycles. [1] Commonly, the first observed feature of pregnancy is the absence of menstrual bleeding. However using last menstrual period is not very useful in determining the gestational age. [13]

Vaginal bleeding following a period of amenorrhea

It's common for pregnant females to bleed on and off during the first trimester[12] and this could be misinterpreted as menstrual bleeding, but bleeding could be due to a spontaneous abortion, ectopic pregnancy, or gestational trophoblastic disease. Therefore it's important to know whether the last menstrual periods were similar to previous ones, and whether she was on any hormonal contraceptive method before coming to conclusion.

It's a very common presentation, and affects about 70%-80% pregnant females.[2] During pregnancy, the blood levels of progesterone is constantly high, and that is suggested to be an adaptation to keep the uterine smooth muscles relaxed until the fetus is mature enough to be delivered. [3] It is also a way to keep the mother away from ingesting potentially harmful substances for the fetus. [6] But as an adverse outcome of this adaptation, relaxation of smooth muscle tissue in the body's other parts give undesirable symptoms. It is also described that human chorionic gonadoptropin and estrogens also play a major role in nausea and vomiting during pregnancy. Overall, the susceptibility for gastrointestinal disturbances are mediated by vestibular, gastrointestinal, olfactory, and behavioral pathways. [4] [5] Hyperemesis gravidarum should always be taken into consideration.

Lower abdominal pain

It could be the first presentation of pregnancy, a benign implantation bleed but could be a warning sign of subchorionic hemorrhage, spontaneous abortion, ectopic pregnancy, heterotopic pregnancy, anembryonic pregnancy, gestational trophoblastic disease, and round ligament syndrome. [7] [8] Apart from the commoner aspects, rarer cases of lower abdominal pain have been reported and cannot be considered lightly. [9] [10]

As an incidental finding during medical checkup.

Especially in women who have irregular menstrual cycles, or been on a selection of contraception, or more commonly who are uneducated about conception. [11]

Examination

Fact

Explanation

Enlarged uterus in bimanual examination

An enlarged uterus can be felt by bimanual palpation even in the first trimester. [1] [3] The gestational age can be assessed through the size of uterus but it is not as accurate as ultrasonography and may lead to unnecessary interventions. [1] [2]

Breast changes.

Increase in size and glandularity is a constant change during pregnancy. It could manifest in early weeks, though the changes are more visible later on. [1] [2]

Hegar's sign

Softening and enlargement of the cervix. Which can be observed at around 6 weeks. [1] [2] [5] [6]

Chadwick sign

Bluish discoloration of the cervix from venous congestion. This can be observed by 8-10 weeks [1] [2]

Palpable uterus low in the abdomen.

Usually later in pregnancy, at least after 12-13 weeks. [1] [2]

Wight, height and body mass index (BMI)

Extremes of pre-pregnancy or first trimester BMI has been associated with adverse fetal outcomes, mainly preterm births. [7] [8] [9]

EVANS, M.F. Diagnosing pregnancy. What is the best way? Can Fam Physician. [online] Feb 1998; 44: 287–289. [viewed April 17, 2014] Available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2277596/pdf/canfamphys00048-0081.pdf

Differential Diagnoses

Fact

Explanation

First trimester miscarriage.

When vaginal bleeding is the presentation, needs to exclude a miscarriage. Researches have shown that heavy bleeding in the first trimester, particularly when accompanied by pain, is associated with higher risk of miscarriage. Spotting and light episodes are not, especially if lasting only 1-2 days. [1]

Ectopic pregnancy.

Most present with missed periods, a lower abdominal pain, and probably vaginal bleeding. Ultrasonography is the gold standard to exclude an ectopic. [2] [3].

HCG secreting pelvic tumors.

Mainly germ cell tumors. Even though not much of a differential diagnosis, it's worthy to consider in atypical presentations because they can mimic some symptoms of pregnancy due to high HCG level, and also can yield false positive results in urine HCG tests. [4] Lower abdominal pain can mimic a ruptured ectopic pregnancy. [6]

Pregnancy luteoma.

It's rare and a benign neoplasm of the ovary which is thought to be caused by the hormonal effects of pregnancy. Usually asymptomatic and an incidental finding at the ultrasonography. [5] This is a benign tumor but other tumors which are not so worthy of ignorance can manifest as a luteoma. [8]

Choriocarcinoma

It can always appear as a soft tissue mass in pregnant females, and sometimes with exaggerated pregnancy features. The females who pose a risk for gestational trophoblastic disease should always be screened for. [7]

Investigations - for Diagnosis

Fact

Explanation

Obstetric ultrasonography

Currently the best and diagnostic investigation, [1] [12] not only for confirmation but to assess the pregnancy in terms of singleton/multiple, site [4] [5], dating [3], and later on follow up with fetal growth monitoring. It is also an important tool in assessing fetal malformations. [2] Excluding an ectopic pregnancy is very essential in suspected individuals. [9]

Urine HCG. (Human Chorionic Gonadotrophin)

It is a glycoprotein synthesized by the syncytiotrophoblast to continue the pregnancy. Detectable in urine in dipstick test two weeks following conception and in blood, even before that. [6] [7] The sensitivity of urine testing is satisfactory. [8] Even with using an extremely sensitive assay for hCG, 10% of clinical pregnancies were undetectable on the first day of missed menses. [11] Negative urine pregnancy testing with the presence of amenorrhea can imply a pathological condition. [10]

Investigations - Fitness for Management

Fact

Explanation

VDRL test. ( Venereal Disease Research Laboratory)

It is a serological screening test to assess whether the patient has been infected with syphilis, though there are many false positives and negatives [3], and with the current higher use of antibiotics the prevalence being low [1], the importance of checking it is that if one person has been infected with one sexually transmitted infection, then she has a higher chance of being infected with other infections as well. So this serves a dual purpose in treating the pregnant females for syphilis [4], and also identifying the risky population, especially for HIV. [1] [2] [5]

Hemoglobin level

Pregnancy is a demanding period of life, because the mother has to nurture another growing human being inside her, with storing nutrition for upcoming nursing period as well as managing her own daily nutrition requirement. Anemia in pregnancy has been associated with fetal adverse outcomes [9] with spontaneous abortions, preterm deliveries and postnatal complications. [6] Anemia has quite a high prevalence in the pregnant females of developing countries. [10] The commonest cause is iron deficiency. [7] But there are other less common but important causes such as malaria. [8] Reasonable analysis and treating as required improves the outcome of pregnancy. [6]

Fasting blood glucose

Fasting blood sugar describes the ability to handle glucose level in between meals, that is to say, the basal insulin action. This can be used as a tool to screen pre-existing diabetes mellitus [11] [12] or impaired fasting glucose which pose a threat to the mother and the fetus both [13]. Early in pregnancy the blood glucose levels tend to fall slightly as a normal physiological reaction. [14] So it is important to use cut-off limits for gestational age of pregnancy. [15]

Oral glucose tolerance test (OGTT)

The estimates insulin sensitivity taken from OGTT is significantly useful than that of fasting glucose level. [16] During pregnancy the anti-insulin hormones ( human placental lactogen, glucagon and cortisol mainly) are grossly elevated, even though insulin level is also doubled, the total effect is relative glucose intolerance. This steadily and progressively increases with gestational age. [17]

Blood group

Screening for Rhesus negative females during first trimester makes it more efficient and cost-effective in using antenatal prophylaxis against Rh incompatibility of the fetus. [18] Prior diagnosing the ABO blood group is important in maternal emergencies.

Urine proteins

Proteinuria/albuminuria is a hallmark feature of pre-eclampsia, and it also screens for pre-existing renal disorders. In females with normal blood pressure, this is to establish a reference level for later uses. [19]

HIV screening

This is not done as a routine investigations but when the female is volunteering to get herself screened, it is a must to do so, and by that prevents fetal adverse outcomes and also vertical transmission of HIV. [20]

Investigations - Followup

Fact

Explanation

Obstetric ultrasonography.

The modified biophysical profile has been found to be an excellent means of fetal surveillance and identifing patients who are at increased risk for adverse perinatal outcome and small-for-gestational-age infants. [1] The frequency depends on the stage of pregnancy and the obstetrician's wishes. Biophysical profile is more accurate in the identification of the hypoxic fetus than any other single method.